The trade was announced Tuesday.
The 26-year-old Lombardozzi hit .288 in 20 games for Baltimore last season, all at second base. The Pirates have invited him to spring training later this month.
The switch-hitting Lombardozzi is a career .266 hitter with Washington and Baltimore.
Last Tuesday, Pittsburgh traded outfielder Travis Snider to the Orioles for a minor league pitcher and a player to be named. The Pirates said Lombardozzi isn't the player to be named from that previous deal.
Baltimore also sent catcher Michael Ohlman to the St. Louis Cardinals for cash. The 24-year-old Ohlman hit .236 with Double-A Bowie last season.